Marine natural products—XV : Polyhalogenated cyclic monoterpenes from the red alga plocamium cartilagineum of antarctica

Examination of the red alga Plocamium cartilagineum (L.) Dixon collected along the Antarctic Peninsula yielded several new cyclic halogenated monoterpenes. The structures of a 2,4-dichloro-trans-1-chloro-vinyl-1-methyl-5-methylene-cyclohexane, a 2-chloro-4-bromo-trans-1-chlorovinyl-1-methyl-5-methylene-cyclohexane, a 2-chloro-trans-1-chlorovinyl-1-methyl-5-chloromethyl-4-cyclohexene, and a 2,5-dichloro-4-bromo-trans-1-chlorovinyl-1-methyl-5-bromomethyl-cyclohexane are described. The structures were determined by spectroscopic methods and chemically related to the halogenated monoterpene violacene.     

Supercritical fluid extraction of halogenated monoterpenes from the red alga Plocamium cartilagineum

Supercritical fluid extraction (SFE) of the marine red alga Plocamium cartilagineum, which is known to contain complex mixtures of halogenated monoterpenes, was investigated. P. cartilagineum samples were extracted by SFE with carbon dioxide and modified carbon dioxide containing up to 10% methanol at different pressure and temperature conditions to establish the optimum conditions for extraction. These conditions were then used in the extraction of halogenated monoterpenes from 2 different samples of P. cartilagineum: one from Davenport, CA, and the other from Casa Beach (San Diego, CA). Several halogenated monoterpenes isolated by conventional solvent extraction with methanol and purified by column chromatography were used as the reference compounds for the determination of the extraction efficiency in the SFE experients. Plocamium cartilagineum belongs to the red alga family--Plocamiaceae, and has been found to contain a large number of halogenated monoterpenes, whose structures typically contain 1-6 bromine and/or chlorine atoms. P. cartilagineum grows along the Pacific coast from Washington to Chile, the British Isles, Australia, and Spain. Interestingly, P. cartilagineum collected from different geographical areas in the world are all reported to produce halogenated monoterpenes, but of different structural types and halogen substitution patterns. Most of these halogenated monoterpenes have been found to exhibit varied biological activities, including antifungal, antimicrobial, and molluscicidal activity.     

Enantioselective Divergent Syntheses of Several Polyhalogenated Plocamium Monoterpenes and Evaluation of Their Selectivity for Solid Tumors

The family of polyhalogenated monoterpenes from Plocamium counts over a hundred known members. Using glyceraldehyde acetonide as a chiral‐pool precursor, an enantioselective and divergent strategy was developed that provides a blueprint for the synthesis of many of the small yet complex acyclic members of this family. The broad applicability of this approach is demonstrated with the short, eight‐step synthesis of four natural products and three analogues. These syntheses are the first of any members of the acyclic polyhalogenated Plocamium monoterpenes and permitted the evaluation of their selectivity against a range of tumor cell lines.     

Widespread occurrence of polyhalogenated compounds in fat from kitchen hoods

Food and contaminated indoor environments are the most relevant sources of human exposure to polyhalogenated chemicals. This study analyzed for the first time fat residues in kitchen hoods for contaminations with polyhalogenated compounds. A wide range of contaminants was detected in all kitchen hoods (n?=?15) and most of them could be quantified. Between 0.2 and 18 μg polyhalogenated chemicals/g fat were detected, with chlorinated paraffins being the most relevant contaminant group. Aside from the chlorinated paraffins, each kitchen hood fat sample showed a distinct fingerprint. A wide range of old and current-use brominated flame retardants were also detected in the samples. In addition to these contaminants originating from their use in indoor equipment, residues of organochlorine pesticides and semi-volatile halogenated natural products verified that cooking of food, accompanied with the release of contaminants from the heated food, was another relevant source of contamination. Re-analyses of two samples after 3 months only resulted in small variations in contaminant pattern and concentrations. Therefore, fat from kitchen hoods is proposed as an easily accessible matrix to assess contamination of these hazardous polyhalogenated chemicals.

An application of the INEPT pulse sequence to the NMR assignment of halogenated marine natural products

The routine use of the INEPT pulse sequence is shown to be the method of choice for the assignment of multiplicity from ¹³C NMR spectra where no prior information about the ¹J(CH) coupling constants is available, or where these are expected to vary over a large range. This technique is illustrated using spectra obtained from polyhalogenated monoterpenes isolated from the red alga Plocamium angustum, which have ¹J(CH) values varying from 127 to 203 Hz.     

Natural Products Produced in Culture by Biosynthetically Talented Salinispora arenicola Strains Isolated from Northeastern and South Pacific Marine Sediments

Laboratory cultures of two ‘biosynthetically talented’ bacterial strains harvested from tropical and temperate Pacific Ocean sediment habitats were examined for the production of new natural products. Cultures of the tropical Salinispora arenicola strain RJA3005, harvested from a PNG marine sediment, produced salinorcinol (3) and salinacetamide (4), which had previously been reported as products of engineered and mutated strains of Amycolatopsis mediterranei, but had not been found before as natural products. An S. arenicola strain RJA4486, harvested from marine sediment collected in the temperate ocean waters off British Columbia, produced the new aminoquinone polyketide salinisporamine (5). Natural products 3, 4, and 5 are putative shunt products of the widely distributed rifamycin biosynthetic pathway.     

Novel monocyclic sester- and triterpenoids from the marine diatom, Rhizosolenia setigera

The structures of two polyunsaturated monocyclic triterpenes have been elucidated using NMR spectroscopy following their isolation from the common marine diatom, Rhizosolenia setigera. The structure of a related monocyclic sesterterpene is proposed on the basis of mass spectral comparisons with the two monocyclic triterpenes.     

The first and efficient synthesis of some of the polyhalogenated benzobarrelenes: unusual formation of a benzosemibullvalene derivative

New polyhalogenated benzobarrelenes were synthesized in good yields. The bromination reaction of benzobarrelenes at high temperature gives non-rearranged products. Dehydrobromination of the formed products with t-BuOK yielded the desired polyhalogenated benzobarrelenes. The elimination reaction of cyclopropanoid dibromide with a base unusually resulted in the formation of a benzosemibullvalene derivative.     

Synthesis of vicinal diols from various arenes with a heterocyclic, amino or carboxyl group by using recombinant Escherichia coli cells expressing evolved biphenyl dioxygenase and dihydrodiol dehydrogenase genes

Various aromatic molecules, in which heterocycles are linked with a phenyl or benzyl group, were converted to their respective 2,3-diols (catechols) in the benzene ring by growing cell reactions using recombinant Escherichia coli, which expressed the evolved biphenyl dioxygenase [bphA (2072)] genes and the subsequent bacterial dihydrodiol dehydrogenase (bphB) gene. These vicinal diol products showed strong in vitro inhibitory activity against the lipid peroxidation induced by free radicals and strong scavenging activity towards DPPH radicals. The vicinal diols were also synthesized from ionized monocyclic aromatics incorporating an amino or carboxyl group.     

Insertion of electrophilic phosphorus into cyclopropanes; a new synthesis of phosphatanes

Electrophilic phosphorus reagents such as [(Cl)(i-Pr₂N)P]⁺ [AlCl₄]⁻ and PhPCl₂/AlCl₃ are found to insert into monocyclic cyclopropanes to yield phosphetanes. The utility of this new method is demonstrated by synthesizing the first phosphetanes bearing phenyl substituents at carbon.     

In Vitro and In Vivo Antidiabetic Potential of Monoterpenoids: An Update

Diabetes mellitus (DM) is a chronic metabolic condition characterized by persistent hyperglycemia due to insufficient insulin levels or insulin resistance. Despite the availability of several oral and injectable hypoglycemic agents, their use is associated with a wide range of side effects. Monoterpenes are compounds extracted from different plants including herbs, vegetables, and fruits and they contribute to their aroma and flavor. Based on their chemical structure, monoterpenes are classified into acyclic, monocyclic, and bicyclic monoterpenes. They have been found to exhibit numerous biological and medicinal effects such as antipruritic, antioxidant, anti-inflammatory, and analgesic activities. Therefore, monoterpenes emerged as promising molecules that can be used therapeutically to treat a vast range of diseases. Additionally, monoterpenes were found to modulate enzymes and proteins that contribute to insulin resistance and other pathological events caused by DM. In this review, we highlight the different mechanisms by which monoterpenes can be used in the pharmacological intervention of DM via the alteration of certain enzymes, proteins, and pathways involved in the pathophysiology of DM. Based on the fact that monoterpenes have multiple mechanisms of action on different targets in in vitro and in vivo studies, they can be considered as lead compounds for developing effective hypoglycemic agents. Incorporating these compounds in clinical trials is needed to investigate their actions in diabetic patients in order to confirm their ability in controlling hyperglycemia.     

Determination of Monoterpenes in Oleoresin: A Chemosystematic Study of the Interaction between Fraser Fir (Abies fraseri) and Balsam Woolly Adelgid (Adelges piceae)

The Fraser fir (Abies fraseri), a conifer native to high elevation sites in the southern Appalachians, has suffered severe mortality attributed to an exotic insect, the balsam woolly adelgid (BWA) (Adelges piceae). Fraser fir, like many other plants, produce volatile organic compounds called monoterpenes in a variety of tissues, including the cortical oleoresin found in blisters on the bark. The purpose of this study was to perform a chemosystematic study to evaluate whether differences in monoterpene composition of Fraser fir oleoresin were observed as a function of the season sampled, the presence or absence of BWA infestation, the health of a tree, and the susceptibility of trees to BWA, based on geographic location. Oleoresin was collected in September and December, 1994, at two mountains, Mount Rogers, where the fir were relatively healthy, and Roan Mountain, where heavy to moderate mortality has been observed. The oleoresin samples were dissolved in methylene chloride, and the monoterpenes were determined by gas chromatography. This method was shown to have acceptable precision for chemosystematic studies for five monoterpenes and the total of all monoterpenes. The levels of monoterpenes in oleoresin were statistically the same for most compounds in September and December, although the total monoterpenes were higher in September at Mount Rogers and α-pinene was higher in December at Roan Mountain. Infested and uninfested fir had the same levels of oleoresin monoterpenes at both mountains. No differences in monoterpene levels were observed at Mount Rogers with healthy and unhealthy fir, but at Roan Mountain, the total monoterpene concentrations were different in these categories. A comparison of monoterpene concentrations in oleoresin from Mount Rogers and Roan Mountain showed statistically significant differences for 3-carene, β-phellandrene, and total monoterpenes.     

Volatile Composition and Biological Activity of Jordanian Commercial Samples of R. coriaria L. Fruits

The present paper reports the GC-HS-SPME analysis of volatile emission and GC-MS analysis of chemical composition of essential oil of R. coriaria fruits of eight different samples of R. coriaria L. fruits (“sumac” folk name), collected from Jordanian agricultural field and the local market. The analyses show an important variability among the Sumac samples probably due to the origin, cultivation, harvesting period, drying, and conservation of the plant material. The main class of component present in all samples was monoterpenes (43.1 to 72.9%), except for one sample which evidenced a high percentage of sesquiterpene hydrocarbons (38.5%). The oxygenated monoterpenes provided a contribution to total class of monoterpenes ranging from 10.1 to 24.3%. A few samples were rich in monoterpene hydrocarbons. Regarding the single components present in all the volatile emissions, β-caryophyllene was the main compound in most of the analyzed samples, varying from 34.6% to 7.9%. Only two samples were characterized by α-pinene as the main constituent (42.2 and 40.8% respectively). Essential oils were collected using hydro-distillation method. Furfural was the main constituent in almost all the analyzed EOs (4.9 to 48.1%), except in one of them, where β-caryophyllene was the most abundant one. β-caryophyllene ranged from 1.2 to 10.6%. Oxygenated monoterpenes like carvone and carvacrol ranged from 3.2–9.1% and 1.0–7.7% respectively. Cembrene was present in good amount in EO samples EO-2 to EO-8. The antioxidant capacities of the fruit essential oils from R. coriaria were assessed using spectrophotometry to measure free radical scavenger 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical and inhibition of β-carotene bleaching (BCB). The essential oils from the fruits of the different samples of R. coriaria exhibited the MIC value ranging from 32.8 to 131.25 µg/mL against S. aureus ATCC 6538 and 131.25 to 262.5 µg/mL against E. coli ATCC 8739. The MIC values of ciprofloxacin were 0.59 and 2.34 µg/mL against S. aureus ATCC 6538 and E. coli ATCC 8739, respectively.     

New study of the essential oil,mineral composition and antibacterial activity of Pistacia lentiscus L. from Eastern Morocco

The present study describes the chemical composition of essential oils of Pistacia lentiscus L., collected from different regions of Eastern Morocco. The essential oils were obtained by hydro-distillation of the areal parts and analyzed by gas chromatography and gas chromatography coupled to a mass spectrometry. The study was conducted to determine the phytochemistry and antibacterial activities of oil from P. lentiscus leaves against both bacteria using the disc diffusion method. For Gram-negative, Salmonella sp., Klebsiella, Escherichia coli, and Pseudomonas, and for Gram-positive, Staphylococcus aureus, and Streptococcus were used as test bacterial strains. In the end, we completed the previous study by determining the minor and major mineral contents of leaves of P. lentiscus. The yield of P. lentiscus oil ranged between 0.13 and 0.23 %, with the chemical composition changing from one region to another. The variations are important between plant populations. The major oil components of PLL oil from Taforalt and Saidia (humid climate) were limonene and α-pinene, while myrcene, β-caryophyllene were found to be the major components of Laayoune and Jerada oil (semi-arid climate). For the mineral composition of PLL, the results show that trace element profiles of leaves from different regions differed significantly; the highest levels of K, Mg, Fe, and Ca were found in leaves of all locations, while the leaves collected from the Jerada region had the highest content of mineral substrates. This work also attempts to contribute to the knowledge of the nutritional properties of this plant; the results will be investigated for the evaluation of dietary information.     

The quinones of bicyclo[3.1.0]hexatriene: A computational study of their chemistry and thermochemistry

Quinones of bicyclo[3.1.0]hexa-1,3,5-triene were examined computationally. The six compounds considered were the five possible classical and one non-classical quinone: bicyclo[3.1.0]hexa-1(6),4-diene-2,3-dione (and its monocyclic isomer with a long trans-annular bond), bicyclo[3.1.0]hexa-1(5),3-diene-2,6-dione, bicyclo[3.1.0]hexa-1,4-diene-3,6-dione (and its monocyclic isomer with a long trans-annular bond), and bicyclo[3.1.0]hexa-1(5),4-diene-2,4-dione-3,6-diyl, a non-classical (non-Kekulé) zwitterion. The two long trans-annular bond structures are akin to that found for m-benzyne. Geometries were calculated (BLYP/6-31G¹, CASSCF(2,2)/6-31G¹, MP2/6-31G¹) and electronic structural inferences were made from the geometries. Also calculated were relative energies and heats of formation (CBS-QB3), singlet and triplet energies (BLYP/6-31G¹), and ionization energies and electron affinities (HF/6-311+G⁷//BLYP/6-31G¹). The NICS(1) calculations were performed as a probe of the aromaticity of the diverse quinones.     

Variability of the Chemical Composition of the Essential Oil from the Amazonian Ishpingo Species (Ocotea quixos)

Ocotea quixos (Lam.) Kosterm. is an aromatic tree native to Ecuador, whose leaves are used to prepare aromatic beverages to which different health benefits are attributed. In this study, Ocotea quixos leaves were collected in the Amazon region in different environmental conditions and subjected to hydrodistillation to isolate the essential oil. The collection variables used were type of soil, amount of shade, and height; in addition, the presence of twig and leaf age and moisture were used as variables. Chemical composition was analyzed by means of gas chromatography equipped with a flame ionization detector and gas chromatography coupled to mass spectrometry. A wide variety of chemical compositions were detected in the samples. In total, forty-seven compounds were identified, which represented between 97.17% and 99.89% of the total composition. The constituents were mainly grouped into aliphatic sesquiterpene hydrocarbons (33.03–55.89%), other compounds (8.94–47.83%), and oxygenated monoterpenes (1.97–39.66%). The main constituents were found to be (E)-cinnamyl acetate (5.96–41.65%), (E)-methyl cinnamate (0.38–37.91%), and trans-caryophyllene (8.77–37.02%). The statistical analysis suggested the existence of two essential oil chemotypes and a direct correlation between environmental conditions and chemical composition of the essential oils.     

Pyranosylmagellanicus a novel structural class of polyhalogenated acetogenins from Ptilonia magellanica

Three naturally occurring pyranosyl-like polyhalogenated metabolites 1-3 as well as their likely biogenetic precursor, the linear compound 4, have been isolated from the red alga Ptilonia magellanica. They are the first compounds within the genus that incorporate chlorine in their network. Compound 3 have structural features reminiscent of the universal chemical signal AI-2 (autoinducer-2) for bacterial communication.     

Secondary Metabolites with Antimicrobial Activities from Chamaecyparis obtusa var. formosana

Seven new compounds, including one dimer novel skeleton, chamaecyformosanin A (1); three diterpenes, chamaecyformosanins B–D (2–4); one sesquiterpene, chamaecyformosanin E (5); and two monoterpenes, chamaecyformosanins F and G (6 and 7) were isolated from the methanol extract of the bark of Chamaecyparis obtusa var. formosana. Their structures were established by the mean of spectroscopic analysis and the comparison of NMR data with those of known analogues. Their structures were elucidated on the basis of physicochemical evidence, in-depth NMR spectroscopic analysis, and high-resolution mass spectrometry. Furthermore, the isolated compounds were subjected to an evaluation of their antimicrobial activity. Metabolites 1, 3, and 4 present antibacterial activities. It is worth mentioning that the chemical composition of the bark of C. obtusa var. formosana has never been studied in the past. This is the first time the barks from C. obtusa var. formosana were studied and two new skeleton compounds, 1 and 7, were obtained.     

Le vibrateur -CH2, un auxiliaire approprié à l'étude structurale des halogéno-cyclopentanones

A study of CH₂, scissors-vibrations of monohalogenated cyclopentanones shows the existence of two conformers in the dissolved state. Similarly structural analysis of some polyhalogenated cyclopentanones has been performed and two conformers found for trans-dichloro-2,5-cyclopentanone. Spectroscopic data collected between 1800-1700 cm^?1 and 1500-1400 cm^?1 are in agreement with a half-chair structure.     

Investigation of monoterpenes complexation with hydroxypropyl-β-cyclodextrin

In this study, we investigated the inclusion complexation of 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) and eight monoterpenes (eucalyptol, geraniol, limonene, linalool, α-pinene, β-pinene, pulegone, and thymol) in aqueous solution and solid state. The formation constants (K _f) of inclusion complexes were determined using fluorescence spectroscopy and static headspace gas chromatography. The results indicated the formation of 1:1 inclusion complexes between HP-β-CD and all studied guests. A linear relationship was found between K _f values and the hydrophobic character of the monoterpenes expressed as logP. Solid complexes were prepared by the freeze-drying method in a 1:1 (HP-β-CD:monoterpene) molar ratio. Physicochemical characterization of solid inclusion complexes was carried out using Fourier transform infrared spectroscopy and differential scanning calorimetry. Finally, the encapsulation efficiency (EE%) of HP-β-CD was determined using HPLC analysis. Noticeable difference in the EE% was observed between monoterpene hydrocarbons and oxygenated monoterpenes. These results suggested that complexation with HP-β-CD could be a promising strategy to enlarge the application of monoterpenes in cosmetic, pharmaceutical and food industries.